Category: Fear

Kentucky, USA. A woman known only as SM is walking through Waverly Hills Sanatorium, reputedly one of the “most haunted” places in the world. Now a tourist attraction, the building transforms into a haunted house every Halloween, complete with elaborate decorations, spooky noises and actors dressed in monstrous costumes. The experience is silly but still unnerving and the ‘monsters’ often manage to score frights from the visitors by leaping out of hidden corners.

But not SM. While others show trepidation before walking down empty corridors, she leads the way and beckons her companions to follow. When monsters leap out, she never screams in fright; instead, she laughs, approaches and talks to them. She even scares one of the monsters by poking it in the head.

SM is a woman without fear. She doesn’t feel it. She has been held at knifepoint without a tinge of panic. She’ll happily handle live snakes and spiders, even though she claims not to like them. She can sit through reels of upsetting footage without a single start. And all because a pair of almond-shaped structures in her brain – amygdalae – have been destroyed.

Ever prodded at an injury despite the fact you know it will hurt? Ever cook an incredibly spicy dish even though you know your digestive tract will suffer for it? If the answers are yes, you’re not alone. Pain is ostensibly a negative thing but we’re often drawn to it. Why?

According to Marta Andreatta from the University of Wurzburg, it’s a question of timing. After we experience pain, the lack of it is a relief. Andreatta thinks that if something happens during this pleasurable window immediately after a burst of pain, we come to associate it with the positive experience of pain relief rather than the negative feeling of the pain itself. The catch is that we don’t realise this has happened. We believe that the event, which occurred so closely to a flash of pain, must be a negative one. But our reflexes betray us.

Andreatta’s work builds on previous research with flies and mice. If flies smell a distinctive aroma just before feeling an electric shock, they’ll learn to avoid that smell. However, if the smell is released immediately after the shock, they’re actually drawn to it. Rather than danger, the smell was linked with safety. The same trick works in mice. But what about humans?

If you wanted to turn a rat into a fearless critter, unfazed by cats or bigger rats, the best way would be to neutralise a small pair of tiny structures in its brain called the dorsal premammillary nuclei, orPMD. According to new research by Simone Motta at the University of Sao Paolo, these small regions, nestled within a rat’s hypothalamus, control its defensive instincts to both predators and other rats.

But not all neurons in the PMD are equal. It turns out that the structures are partitioned so that different bits respond to different threats. The front and side parts (the ventrolateral area) are concerned with threats from dominant and aggressive members of the same species. On the other hand, the rear and middle parts (the dorsomedial area) process the threats of cats and other predators. And both areas are distinct from other networks that deal with the fear of painful experiences, such as electric shocks.

This complexity is surprising. Until now, scientists have mostly studied the brain’s fear system by focusing on an area called the amydgala, which plays a role in processing memories of emotional reactions. And they have generally assumed that fearful responses are driven by the same networks of neurons, regardless of the threat’s nature.

There’s good reason to think that. Hesitating in the face of danger is a sure-fire way to lose one’s life, so animals respond in a limited number of instinctive ways when danger threatens. They freeze to avoid detection, flee to outrun the threat, or fight to confront it. These automatic “freeze, fight or flight” responses are used regardless of the nature of the threat. Rats, for example, behave in much the same way when they are menaced by cats or electrified floors alike, and actually find it very difficult to do anything else.

This limited repertoire of action convinced scientists that animals process different fears in the same way, relying on the same network of neurons to save their hides from any and all threats. Motta’s research shows that this idea is wrong, certainly for rats and probably for other mammals too. The brain’s fear system isn’t a one-size-fits-all toolkit; it has different compartments that respond specifically to different classes of threats.

Propranolol is commonly used to treat high blood pressure and prevent migraines in children. But Merel Kindt and colleagues from the University of Amsterdam have found that it can do much more. By giving it to people before they recalled a scary memory about a spider, they could erase the fearful response it triggered.

The critical thing about the study is that the entire memory hadn’t been erased in a typical sci-fi way. Kindt had trained the volunteers to be fearful of spidery images by pairing them with electric shocks. Even after they’d been given propranolol, they still expected to receive a shock when they saw a picture of a spider – they just weren’t afraid of the prospect. The drug hadn’t so much erased their memories, as dulled their emotional sting. It’s more like removing all the formatting from a Word document than deleting the entire file.

To quote the person who actually did the research (and thanks Merel for chiming in on the earlier post):

“There was no memory erasure, just elimination of the fearful response.”

The problem with all of this, of course, is that people have straw-manned the research and are falling over themselves to publish trite editorials that (a) are irrelevant to the actual study and (b) serve to stoke public outrage over an ethical dilemma of their own concoction.

There are exceptions. The Boston Globe got it right and has a brilliant bit at the end that lays out in four simple sentences the bottom line, cautions, what’s next, and where the research was published. It has however accompanied the article with an incongruous photo of a koala, presumably some sort of mix-up with the Australian bushfire story.

The mental health charity MIND released a long and well-considered statement, which showed that they had actually read the paper and understood the science. The charity’s CEO, Paul Farmer, said:

“This is fascinating research that could transform the treatment for phobias and post traumatic stress disorder. Around 10 million people in the UK have a phobia and about 3.5% of the population will be affected by post traumatic stress disorder at some point yet our understanding of how to treat these conditions is still limited. While we welcome any advancement in this field we should also exercise caution before heralding this as a miracle cure.

“Eradicating emotional responses is clearly an area we would need to be very careful about. It could affect people’s ability to respond to dangerous situations in the future and could even take away people’s positive memories. We would not want to see an ‘accelerated Alzheimer’s’ approach.

“We still have limited research on how to treat complex mental health problems, with the focus often on pharmacological solutions. Drugs are a somewhat sledgehammer approach and can have unintended consequences. We know from other psychiatric drugs, for example antipsychotics and antidepressants, that individuals react in hugely varied ways to treatments and are often vulnerable to unpleasant side effects.

“We would need to see much more research into the risks and benefits into this treatment before it becomes a reality.”

We like to idolise fearlessness and we equate it to bravery but there is a fine line between that and stupidity. Immunity to the pangs of fear would leave someone unable to assess threats to themselves and to other people, which means that fear not only has consequences for an individual but for their entire social circle. Guillaume Martel and colleagues from Rutgers University demonstrated these far-reaching consequences by examining a special group of mice which had been genetically engineered to be fearless.

Martel’s team focused their attention on the amygdalae, a pair of almond-shaped structures, one in each half of the brain, that play an important role in emotion, and particularly in creating and storing memories linked to emotional events. Each amygdala can be divided up into a few distinct regions depending on their role and which other parts of the brain they connect to. One of these regions – the basolateral complex, or BLA- is specifically involved in learning about fear.

The team worked with mice that were missing a gene called stathmin, which is particularly active in the basolateral amygdala. In previous research, they had already showed that removing this gene switches interferes with a mouse’s ability to fear. Not only are they inherently bolder than their normal littermates, they also fail to record long-term memories about frightening experiences.

This time, Martel showed that the loss of stathmin also turns female mice into neglectful ones. In a normal situation, a virgin female would react strongly to the sight of abandoned pups, even foster ones. If three isolated pups are placed in the far corner of a female’s cage, she would quickly bring them over to her nest within about three minutes. But not if her basolateral amygdalae isn’t working properly -the stathmin­-less mice took much longer (about 10 minutes or so) to retrieve the pups.

Show someone a piece of rotting food and their reaction will be visibly similar the world over. Their eyes will close, their noses will wrinkle and their mouths will tighten, all part of a universal expression of disgust. Darwin himself was struck by the universal nature of human facial expressions – from the busiest of cities to the most isolated of villages, smiles and frowns are recognisable, done in the same way and carry the same meaning.

Facial expressions are massively important for the social lives of humans and it should come as no surprise that some parts of our brain are dedicated to interpreting the small shifts in facial muscles that betray our emotions. In this light, it makes sense that expressions should be universal, but that doesn’t tell us why they take the form they do. Why is it a smile that indicates happiness and not anger, or why should wide eyes signify fear or surprise and not disgust?

A new study reveals part of the answer and shows that it’s not an arbitrary fluke that certain emotions are tied to specific movements of our facial muscles. Joshua Susskind from the University of Toronto has found that expressions of fear and disgust are adaptive and serve to alter the experiences of our senses.

Fear creates a need for watchfulness to detect potential threats and fearful expressions help with this by widening the eyes and nostrils to increase the information available to the senses. The opposite is true for disgust, which is more about rejecting information that you don’t want. And accordingly, disgusted expressions serve to restrict our perceptions.